Three-dimensional image capturing device

Abstract

A three-dimensional image capturing device comprises a light source irradiating a pulsed light beam, which is reflected by a measurement subject to generate a reflected light beam pulse. In a first distance information sensing operation, a first reflected light component (E 1 ), which corresponds to a distance from the device to the measurement subject and contains a fall of said reflected light beam pulse, is sensed. In a second distance information sensing operation, a second reflected light component (E 2 ), which corresponds to the distance and containing a rise of the reflected light beam pulse, is sensed. The lengths of periods for sensing the reflected light components are identical. A normalized distance information is obtained by calculating (E 1 )/(E 2 ).

What is claimed is:  
     
       1. A three-dimensional image capturing device, comprising: 
       a light source that irradiates a distance measuring light beam, which irradiates a measurement subject and is a pulsed beam, said measurement subject reflecting said distance measuring light beam to generate a reflected light beam pulse;  
       a first distance information sensing processor that senses a first reflected light component (E 1 ) for a first reflected light sensing period, said first reflected light component corresponding to a distance from said device to said measurement subject and containing a fall of said reflected light beam pulse;  
       a second distance information sensing processor that senses a second reflected light component (E 2 ) for a second reflected light sensing period, said second reflected light component corresponding to said distance and containing a rise of said reflected light beam pulse, the length of said reflected light sensing period being equal to that of said first reflected light sensing period; and  
       a normalized distance information calculating processor that obtains a ratio (E 1 )/(E 1 +E 2 ), which is obtained by dividing said first reflected light component (E 1 ) by a sum of said first and second reflected light components (E 1 +E 2 ), as a normalized distance information corresponding to said distance.  
     
     
       2. A device according to  claim 1 , further comprising an ambient daylight sensing processor that senses an incident light, which is an ambient daylight component around said measurement subject, for an ambient daylight sensing period the length of which is equal to those of said first and second reflected light sensing periods, while said light source is turned OFF, said normalized distance information calculating processor obtaining said ratio, using calculation components, which are obtained by subtracting said ambient daylight component from said first and second reflected light components, respectively. 
     
     
       3. A device according to  claim 2 , wherein a sensing operation of said ambient daylight sensing processor is performed between sensing operations of said first and second distance information sensing processors. 
     
     
       4. A device according to  claim 1 , wherein each of said first and second distance information sensing processors comprises: 
       a plurality of photoelectric conversion elements in each of which electric charge corresponding to an amount of said reflected light component is accumulated;  
       a signal charge holding unit disposed adjacent to each of said photoelectric conversion elements;  
       an electric charge discharging processor that discharges unwanted charge accumulated in each of said photoelectric conversion elements, so that an accumulating operation of signal charge is started in each of said photoelectric conversion elements;  
       a signal charge transfer processor that transfers said signal charge accumulated in said photoelectric conversion elements to said signal charge holding unit; and  
       a signal charge integrating processor that drives said electric charge discharging processor and said signal charge transfer processor alternately, so that said signal charge is integrated in said signal charge holding unit to sense said distance.  
     
     
       5. A device according to  claim 2 , wherein said ambient daylight sensing processor comprises: 
       a plurality of photoelectric conversion elements in each of which an electric charge corresponding to an amount of said incident light is accumulated;  
       a signal charge holding unit disposed adjacent to each of said photoelectric conversion elements;  
       an electric charge discharging processor that discharges unwanted charge accumulated in each of said photoelectric conversion elements, so that an accumulating operation of signal charge is started in each of said photoelectric conversion elements;  
       a signal charge transfer processor that transfers said signal charge accumulated in said photoelectric conversion elements to said signal charge holding unit; and  
       a signal charge integrating processor that drives said electric charge discharging processor and said signal charge transfer processor alternately, so that said signal charge is integrated in said signal charge holding unit to sense distance correction information corresponding to an amount of said ambient daylight component.